Multi-purpose suction anchor with interior access doors

ABSTRACT

An improved reusable suction anchor, method of using this suction anchor, and method of manufacturing this suction anchor which uses doors to provide access to the interior of the anchor, by ROV or crane operated shovel for example. It provides a simple way to eliminate piping or plugging. It provides a simplified way to install or maintain a blowout preventer. It also provides a simplified way to align various diameters of pipe and to install conductor pipe. It also provides storage and protection from falling objects.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Provisional Application titled: AMethod For Containing an Underwater Oil Leak and Protecting theEnvironment, filed on May 12, 2010 by Richard M. Evans.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention is not the result of any federally sponsored research ordevelopment. Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention is an improved suction anchor. Suction anchors are usedby various offshore industries as moorings for various offshorestructures or vessels. The offshore petroleum industry is a primary userof such anchors. This background information frequently mentions use bythe petroleum industry. However, the use of suction anchors is notlimited to the petroleum industry. For example, wind turbines can beanchored at sea using suction anchors.

Subsea suction anchors are commonly used in the offshore petroleumindustry to moor or anchor offshore structures. These suction anchorsmay also be known as suction piles or suction caissons. Often, but notalways, these suction anchors are essentially a cylindrical tube withone end closed by a top plate and one end open. Cylindrical anchors arecircular in cross section, but other anchors may be rectangular, oval,hexagonal, or any number of other closed shapes in cross section. A pumpis used to depressurize or pressurize the interior so the anchor movesinto or out of the sea floor soil. What is essential is that they mustnot collapse when the required stresses are placed on them, and thatthey must remain anchored to the sea floor when stresses are applied. Acommonly used method for installing suction anchors involves loweringthem to a point near the sea floor. In preparation for dropping theanchor, valves are opened to allow water to evacuate the interior of theanchor. Tension on the attached cables is greatly reduced, and theanchor is allowed to fall in a controlled drop to the sea floor. Theweight and momentum of the heavy anchor drives it partially into thesubsurface soil.

When the anchor is dropped, even open valves resist the downward motionsomewhat. This resistance reduces the speed of the dropping anchor andtherefore reduces the depth of self weight penetration. This self weightpenetration is usually only partial, and additional means are needed toforce the anchor to fully imbed into the soil. In the case of suctionanchors, suction penetration is used. A pump is attached to the suctionanchor. Water is pumped out of the interior of the anchor. This causes adifferential water pressure on the interior and exterior of the suctionanchor. The desired result is that this differential pressure forces thesuction anchor deeper and deeper into the sea floor until a desireddepth is attained. Problems are known which hinder or stop the anchorfrom achieving the desired penetration depth. Instead of furtherimbedding the anchor, suction may cause soil to be pulled upward intothe tube of the anchor. This problem is known as piping or plugging.Certain subsea soil conditions increase the chance of piping orplugging. A top layer of silt, among other soil problems, may increasethe likelihood of this problem, and cause the anchor to fail to fullypenetrate the soil. A partially installed anchor could not be reliedupon, and could pull out of the subsurface with dangerous results. Asubmersible remotely operated vehicle, ROV, might suction awayundesirable subsea soil inside the anchor with a pump if it could accessits interior. Current suction anchors have no way for an ROV to gainsuch access to the interior of the installed or partially installedsuction anchor. Alternately, a surface vessel could lower a clamshellshovel or other device to remove undesirable soil from the interior of asuction anchor. However, current suction anchors provide no means toaccess the interior of the anchor to do so. Also, an ROV or surfacevessel might replace undesirable contents with desirable contents insidethe anchor if it could access the interior of the suction anchor. Again,current suction anchors provide no means to enter the anchor to do so.

Another requirement of the petroleum industry is perfect alignment. Forexample, in the early stages of drilling a well, conductor pipe isinstalled below the subsea surface. This conductor pipe has a largediameter. This pipe must be perfectly aligned before it is installed.The next section of conductor pipe must be perfectly aligned with thefirst before it can be installed, and so forth. In later stages ofdrilling, blowout preventers, drilling pipe and casing pipe must also beperfectly aligned in order to be installed or used. Unfortunately all ofthese objects have different diameters. The blowout preventer is verylarge. Drilling pipe has a small diameter. A suction anchor at thewellhead might have an access port of the correct diameter to help alignconductor pipe. But this port could not also align a blowout preventer,or permit it to be lowered beyond the level of the port. Such a portwould also be the incorrect diameter for aligning a drill pipe string orcasing pipe string. Hydraulic arms on an ROV might be useful foraligning a blowout preventer for installation. However, hydraulic armsor jacks must have something to press against or to attach to. Althoughit would be useful for an ROV to enter the interior of a suction pile,current technology does not provide a means for it to do so.

A pipe, drill bit, or other tool might become damaged below the subseasurface. To replace such damaged equipment is a lengthy process. A pipestring would be hoisted upward to the surface structure. One by one,each pipe in the pipe string would have to be disassembled. Then thenext pipe would be raised and disassembled until the faulty piece ofequipment finally was brought to the surface. It would be replaced andthen the process would be reversed. Pipe after pipe would be attachedand lowered step by step to the seafloor level and below. If an ROVcould replace damaged equipment at the sea floor level it could providea great savings in time and money. For example, a subsea wellhead mightbe 1 mile below the sea surface. If an ROV could replace a piece ofdamaged equipment at the sea floor level, raising and lowering the pipestring one mile in each direction could be avoided. Lateral or verticalmotion of the pipe string would hinder such an operation. An ROV mighthold a pipe string in alignment for such an operation, or a port in thetop of a suction anchor might hold the pipe string in alignment. Astrong suction anchor might temporarily hold the weight of the pipestring to avoid vertical movement. In any case, the ROV would need toaccess the damaged part above the blowout preventer and below the top ofthe suction anchor. No means for such access is available in currenttechnology.

Pressurizing or depressurizing a doored suction anchor would raise orlower the anchor. This up/down motion would have great force. It couldbe used to drive a pile or a string of conductor pipe into the sub soil.

The interior of a suction anchor could be used for storage. A wide rangeof equipment might be stored inside. Such storage would be uselesswithout access to the interior. No access is currently available.

Another problem that can occur in the offshore industry is surfaceaccidents. A surface accident can cause heavy objects or debris to fallto the sea floor. If such an accident occurred on an offshore structure,it would likely occur directly above a subsea wellhead. Falling debriscould fall near or directly onto critical components, such as a subseablowout preventer or other critical equipment. It is desirable toprotect critical equipment. But it is also desirable to have access tosubsea components to inspect them, to check gauges or instruments, toremove and replace faulty parts, and so forth. A remotely operatedvehicle, ROV, could be used for all of these purposes. A blowoutpreventer or other equipment placed inside a typical suction anchorwould be protected, but not accessible. A blowout preventer notsurrounded by a suction anchor would be accessible, but less protected.

An advantage of suction anchors is that they are reusable. When they areno longer needed at a location, they can be extracted from the soil andmoved to a new location. To extract the anchor, a pump is typicallyused. It is attached to the suction anchor. For removal of the anchor,water is pumped into the interior of the anchor. The pressuredifferential forces the anchor upward and out of the sea floor soil. Itcan then be moved to a new location and reused.

2. Prior Art

U.S. Pat. No. 6,910,831 B2 Jun. 28, 2005 lists very many publicationsrelated to suction anchors in its “OTHER PUBLICATIONS” section. The samepatent lists several U.S. patents and two foreign patents. These are inits “References Cited” section. These patents are listed here:

-   -   U.S. Pat. No. 3,852,969 A    -   U.S. Pat. No. 4,131,166 A    -   U.S. Pat. No. 4,185,694 A    -   U.S. Pat. No. 4,690,586 A    -   U.S. Pat. No. 4,702,047 A    -   U.S. Pat. No. 5,033,908 A    -   U.S. Pat. No. 5,127,767 A    -   U.S. Pat. No. 6,122,847 A    -   U.S. Pat. No. 6,457,908 B1    -   GB 1269599    -   WO 99/25606

U.S. Patent Application No. U.S. 2008/0292409 A1, dated Nov. 27, 2008refers to two other patents in its paragraphs 0002 and 0003. These arelisted here:

-   -   U.S. Pat. No. 4,318,641    -   U.S. Pat. No. 6,719,496

U.S. Pat. No. 4,432,671 cites the following patents in its “CITATIONS”section:

-   -   U.S. Pat. No. 983,808    -   U.S. Pat. No. 3,263,641    -   U.S. Pat. No. 3,496,900    -   U.S. Pat. No. 3,965,687    -   U.S. Pat. No. 4,036,161    -   U.S. Pat. No. 4,318,641

U.S. Pat. 4,432,671 also lists many patents that it is referenced by.Many of these may be relevant to this patent.

U.S. Pat. 4,575,282 is also a type of suction anchor.

The Wikipedia “Caisson” article shows a caisson which is entered bypeople. However, the caisson does not use pumping means to lower morethan 30% of an anchor body into a sea floor soil or to raise more than30% of an anchor body out of the sea floor. Also, it uses an air lockrather than a door. Also it is meant to be used in very shallow waterwhere people can survive. It uses a pressure differential to keep waterout of the interior. It is not a suction anchor It has a differentpurpose and use than the invention described here.

BRIEF SUMMARY OF THE INVENTION

This is an improved reusable suction anchor, method of using thissuction anchor, and method of manufacturing this suction anchor. Itprovides access to the interior of the anchor, by ROV or crane operatedshovel for example, using doors and gaskets. It provides a simple way toeliminate piping or plugging. It provides a simplified way to install ormaintain a blowout preventer or to replace damaged parts at the seafloor rather than at the sea surface. It also provides a simplified wayto align various diameters of pipe and to install conductor pipe. Italso provides storage and protection from falling objects. It provides amethod to contain an uncontrolled underwater oil leak, as a backup to anon-functioning blowout preventer, especially if it is installed beforethe uncontrolled oil leak occurs.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

None of the illustrations are meant to limit the size, location, number,or type of doors, latches, latch catches, opening and closingmechanisms, attachment points, holes, throughput ports, valves, or mudfins illustrated. They are also not meant to limit the shape or size ofthe body of the anchor. The illustrations only show possible embodimentsof the invention.

FIG. 1 illustrates a suction anchor that is generally a rectangularprism in shape. Example locations of hinged and unhinged doors and dooropenings are shown. Example door opening and closing means, gaskets,latches, ports, holes, valves, or attachment points are also shown.

FIG. 1A is a cutaway view of FIG. 1 with two notable differences. A widelip at the top is a part of the suction anchor body. The lip wouldlikely have a gasket attached to its underside and top side. A hingeddoor has also been added. Its hinge has been attached below the lip andit hangs downward, almost vertically, inside the anchor body when it isopen. Note that this door would close as the top of the anchor body camevery close to the sea floor. As the body was being suctioned downward,the door would contact the sea floor and be pushed upward and closed.

An interior hung door might be used as follows: In order to reuse asuction anchor, it must be pulled out of the sea floor and moved to anew location. The interior door of FIG. 1A would be closed. Water wouldbe pumped into the interior. Water pressure would push the door upwardagainst the lip and gasket to pull the whole suction anchor upwards outof the soil. (Other interior doors, not shown in FIG. 1A, might alsoclose against other door openings on the inside of the body.)

Interior doors might also be unhinged, but these are not illustrated.

Referring initially to FIG. 1, the improved suction anchor is a suctionanchor with added access doors. Gaskets are located at the areas wherethe doors meet the body of the anchor when closed. A rectangular suctionanchor is illustrated, but the anchor need not be rectangular. Thesuction anchor illustrated is an anchor body 1 attached to varioushinged doors 6,12 and unhinged doors 2, 21. Previous suction anchorshave had an attached, immovable top plate which was an integral part ofthe anchor. The illustrated version has no immovable top plate. The topplate function can be replaced by closing either hinged door 6 or 12.Gaskets are shown for maintaining a differential pressure inside andoutside the body and doors. Gaskets would likely be attached to the topof the body 17 and the sides of the body 22 and 26 where closed doorscontact the body. Gaskets might instead be attached to the doorsthemselves at locations 9, 10, or inside the unhinged doors 2 and 21 atlocations not illustrated. Gaskets could also be attached at all ofthese locations. Possible locations of motors 4, 19 for opening orclosing doors are illustrated. Additional possible door openingmechanisms 3, 20 are shown. Possible locations for door latches 11,27and latch catches 5, 18 are also shown. An ROV might also use latch 11or 27 as an attachment point to open or close door 6 or 12. 7,8,13,14,15and 16 are possible locations for valves, throughput ports, holes,screens, flanges or attachment points. For example, 7, located at thecenter of door 6, might be a hole or throughput port with a diameterjust slightly larger than the diameter of a conductor pipe. When door 6is closed, hole 7 could guide and align conductor pipe as it is lowered.Door 2 might be opened to allow access by an ROV to further guide andalign the bottom of that section of conductor pipe. After conductor pipewas installed all doors might be opened to install the blowoutpreventer. 15 might be a hole or port located at the center of door 12.If port 15 was just slightly greater in diameter than drilling pipe,with door 12 closed, port 15 could then be used to align and guidedrilling pipe as it was lowered or raised. Alternately, 7 and 8 might beone way valves which are the same size.(different than illustrated).When door 6 was closed, an ROV might attach a pump skid to valves 7 and8 to pressurize or depressurize the interior of the suction anchor. Thereal purpose of 7,8,13,14, 15, and 16 is to show that very manydifferent locations and combinations for valves, throughput ports,holes, flanges, screens or attachment points in, on, or through thedoors are possible. It is also possible that one of the doors 6,12 mightbe solid with no valves, throughput ports, holes, flanges, screens orattachment points. (Not illustrated.) It is also possible that anunhinged door 2,21 might have valves, throughput ports, holes, flanges,screens or attachment points in, on, or through it. (Also notillustrated in FIG. 1) Mud fins are shown at 23 and 25. Mud fins mightor might not be attached to the body of the suction anchor 1. These finsmight be located anywhere on the body to limit the depth of penetrationinto the soil. A blowout preventer is shown at 24. The suction anchormight or might not be located at a blowout preventer location. However,if it was, this improved suction anchor would provide many advantageswhich are described elsewhere in this application. 28 and 29 are doorhinges.

In FIG. 1A, 30 is a wide rim that is the top portion of a suction anchorbody similar to that shown in FIG. 1 Also, an interior mounted hingeddoor 31 has been added. The hinge 35 has been attached below the rim onthe interior of the anchor body. It is shown as a dotted line. The door31 is hanging at a near vertical position. 32 is a gasket attached tothe top of door 31. 36 is a gasket attached below the rim. 38 is alatch. 37 is a latch catch. 33 and 34 are representative attachmentlocations for possible valves, holes, vents, throughput ports, screens,or flanges. These locations could also be on the body of the anchor, butare not illustrated. 1, 6,7,8,9,12,13,14,15, and 17 are the same asdescribed in the FIG. 1 description,

DETAILED DESCRIPTION OF THE INVENTION

The invention is an improved suction anchor which has a door or doors.The door or doors provide access to the interior of the suction anchor.The door or doors also provide improvements in the ability to avoidplugging or piping, alignment ability, conductor pipe installation, piledriving, use of walls as a base for pressing against or pulling on,replacing parts at the sea level rather than at the surface, protectionof critical components, storage, and the ability to control anuncontrolled oil leak as a backup to a non-functioning blowout preventer(BOP). All of these are explained below.

Conventional suction anchors are well known. They consist of a body orskirt member which has a permanently attached top plate. The anchor istypically dropped and its weight and momentum drive the lower portion ofthe body partially into the subsea soil. A pump is attached and pumpswater out of the interior of the anchor body. This creates adifferential pressure on the inside and outside of the suction anchor.The greater pressure above presses the anchor deeper into the soil.

In the present invention a door or doors are provided in the suctionanchor. The top plate itself may or may not be replaced by a door. Aportion of the top plate may or may not be cut away and replaced by adoor. A portion of the body may or may not be cut away and replaced by adoor. A door or doors might be hinged or unhinged.

It is desirable to retain the ability to hold a differential pressure.In order to do so, a seal is provided. The seal would be placed where adoor or doors meet the body or top plate of the suction anchor. The sealwould likely be a gasket or gaskets. The gasket or gaskets would beplaced at the location where a door meets the body or top plate of thesuction anchor. Gaskets could be attached to the body, door, or topplate portion of the anchor. Gaskets might be placed at all or some ofthese locations.

Door opening and closing means may be an integral part of the anchor. Ifso, the means would likely be a hydraulic or electric motor attached tothe suction anchor body, top plate, or door. A submersible remotelyoperated vehicle (ROV) could attach a pump to operate a hydraulic motorto open or close the door or doors. An ROV could attach electric cablesor wires to operate an electric motor to open or close doors.Alternately, the opening and closing means might be an ROV. The ROVcould attach to the door or latch and open or close the door. The wholeROV, while attached, might be raised or lowered by a winch on a surfacevessel, attached to the ROV by an elongate member such as a cable orchain, in order to open or close doors. The ROV, while attached, mightuse its own propeller power to open or close a door or doors. The ROVcould attach an elongate member to the door or latch. The top end of theelongate member could be winched up or down from the winch on a surfacevessel to open or close the door or doors. Any combination of openingand closing means might be used to open or close multiple doors.

The door or doors might have valves, throughput ports, holes, screens,attachment points, or flanges attached or as an integral part of thedoor or doors. A door or doors might have a single valve, throughputport, hole, attachment point, screen or flange. A single door might haveany combination of valves, throughput ports, holes, attachment pointsscreens, or flanges. Multiple doors might have any combination ofvalves, throughput ports, holes, screens, attachment points or flanges.

The doors in FIGS. 1 and 1A are flat and essentially planar. Doors neednot be flat or planar. For example, a top door might be spherical,domed, or pyramidal in shape in order to bear a heavier load. On acylindrical body, a side door might be a part of a cylinder. On ahexagonal body, a side door might be a part of a hexagonal prism, forexample.

In FIG. 1, the suction anchor is located at a blowout preventer. Thisinvention has many benefits at other locations as well. The benefits atany underwater location will be mentioned first.

This invention helps avoid or eliminate piping or plugging. The dooredsuction anchor would normally be dropped into the sea floor soil withthe top door or doors open. This would cause less friction than openvalves in a top plate. Therefore the doored anchor would fall faster andpenetrate the sea floor to a deeper depth. If the suction anchor wasbeing used in an area where plugging or piping was a problem,undesirable silt or soil could then be removed from the interior. An ROVcould enter the interior of the anchor through a door. It could use apump to suction or blow out undesirable material. If desirable materialhad previously been lowered from a surface vessel, It could then replacethe undesirable material with desirable material using a pump.Alternately, a surface vessel could lower a clamshell shovel to removeundesirable material from the interior of the suction anchor. An ROVmight use its arms to guide the shovel to correct alignment before theshovel was dropped. Or it might communicate with the surface vessel therequired corrective movements. If desirable material had previously beenlowered, the clamshell shovel could then replace the undesirablematerial with desirable material.

The benefits of this invention at a wellhead or blowout preventerlocation are discussed here.

The benefits just mentioned would also apply at a blowout preventerlocation.

Early in an undersea drilling operation conductor pipe must beinstalled. Installation of conductor pipe is first discussed here.Conductor pipe has a wide diameter. Imagine a suction anchor similar toFIG. 1 partially imbedded in the sea floor. A top door with a centerhole just large enough to accommodate the conductor pipe would beclosed. The pipe would be slowly lowered into the hole. A conical flangemight be attached to the top of the door to help guide the pipe into thehole as it is lowered. An ROV attached to the suction anchor body, door,or top plate might also assist in guiding the pipe as it was lowered. Asthe lower end of the pipe approached the sea floor, the ROV could entera side door (Such as door 2 in FIG. 1.) The ROV could attach to or pressagainst the inside of the anchor walls and further guide or align thepipe as it was lowered. The pipe could then be forced into the subseasoil by currently available means. The use of the doored anchor as aguide or base for the ROV to press against or attach to is new. The ROVcould perfectly align the top pipe with the pipe below so a goodconnection could be made. The ROV might enter the suction anchor toattach extendable arms between the conductor pipe and attachment pointson the walls of the suction anchor. Then with the doors closed a pumpcould pressure the suction anchor up or down. Conductor pipe or a pilecould be driven down in this way. After all conductor pipe wasinstalled, a blowout preventer, BOP, would need to be installed. All topdoors would be opened for this operation. The ROV could attach to orpress against the body of the anchor and against the BOP with itshydraulic arms. The ROV would carefully guide the BOP as it was loweredso it would have perfect alignment. The interior of the doored anchorwould provide a base for the ROV to press against. Doors with adifferent diameter opening could then be closed and used to guide drillpipe or other pipe in a similar manner.

After a well was producing, operators might want to leave the suctionanchor in position, as shown in FIG. 1. The walls and doors couldprovide protection for the BOP. They could deflect any objects moving inthe current or dropped from a structure or vessel above. A suctionanchor, probably with a longer lower half imbedded in the sea floor,could remain under water surrounding the blowout preventer, similar toFIG. 1. If there was a blowout and the blowout preventer failed tofunction, all doors could be closed, containing the pressurized leakingoil inside, until other means could permanently seal off the well.During normal operations, doors would provide access for an ROV toinspect, read gauges, carry out maintenance, replace parts, and soforth.

A spare drill bit or other spare parts could be stored inside thesuction anchor. If a drill bit needed to be replaced, the drill stringcould be raised until the old drill bit was above the BOP but below thetop of the suction anchor. The ROV could enter the suction anchor andattach to its side. With another arm or arms it could disconnect the olddrill bit and replace it with a new one. This would eliminate the needto bring the whole pipe string to the surface to do this task, savingtime and money. The ROV could replace pipe or other parts at the seafloor level as well.

1. A suction anchor comprising: an anchor body pumping means to create adifferential pressure for the purpose of imbedding over 30% of theanchor body into the sea floor soil or lifting over 30% of the anchorbody out of the sea floor soil. a door or a multiplicity of doors toprovide a method for entering or exiting the interior cavity of thesuction anchor using door means. seal means at the location where saiddoor or multiplicity of doors come into contact or near contact with theanchor body when they are closed, to retain said differential pressurewhen the door or multiplicity of doors are closed moving means to openor close said door or multiplicity of doors.
 2. The suction anchor ofclaim 1 where said seal means is gasket means.
 3. The suction anchor ofclaim 1 where said moving means is a motor powered device or amultiplicity of motor powered devices.
 4. The suction anchor of claim 1where said moving means is an engine powered device or a multiplicity ofengine powered devices.
 5. The suction anchor of claim 1 which alsocomprises one or more items from the following list: valve, throughputport, hole, flange, attachment point, screen or vent.
 6. A method forusing the suction anchor of claim 1 which includes the use of a remotelyoperated vehicle (ROV) or a multiplicity of ROVs, using ROV means.
 7. Amethod for using the suction anchor of claim 1 which includes the use ofa shovel or a multiplicity of shovels.
 8. A method for using the suctionanchor of claim 1 which includes a hydraulic motor or multiplicity ofhydraulic motors.
 9. A method for constructing the suction anchor ofclaim
 1. 10. A method for constructing the suction anchor of claim 2.11. A method for constructing the suction anchor of claim
 3. 12. Amethod for constructing the suction anchor of claim
 4. 13. A method forconstructing the suction anchor of claim
 5. 14. A method of using thesuction anchor of claim
 1. 15. A method of using the suction anchor ofclaim
 2. 16. A method of using the suction anchor of claim
 3. 17. Amethod of using the suction anchor of claim
 4. 18. A method of using thesuction anchor of claim
 5. 19. A method of removing undesirable materialfrom in or near the suction anchor of claim
 1. 20. A method of addingdesirable material into or near the suction anchor of claim 1.